1. Field of the Invention
The present invention relates to a serial, bidirectional data transmission method for communication between a programming apparatus and a user apparatus to be programmed, in particular a hearing aid, and a circuit for implementing the data transmission method. In addition, the present invention relates to a hearing aid using such a circuit.
2. Description of the Prior Art
Known data transmission methods of the above type between a programming apparatus and a user apparatus require a number of connecting leads. The interface specified in German 43 21 788 for serial data transmission between a hearing aid and a control apparatus has several data connecting leads for bidirectional data transmission. This known interface requires a first data connection for bidirectional transmission to or from the hearing aid, as well as a second data connection for a data format sent by the control apparatus with a start bit, in addition to a third data connection for the data to be received from the control apparatus. The use of multiple connecting leads produce an increased susceptibility to disturbances due to longer signal paths in the programming of user apparatuses, and also are considered to be disturbing by the users of the apparatuses, particularly in the programming of hearing aids.
From German AS 25 43 130, a circuit arrangement is known for the transmission of digital data in full duplex operation between at least two stations. According to this circuit arrangement for transmitting digital data in full duplex operation, the simultaneous transmission and reception of data via a single signal line, and a number of stations, provided respectively with at least one transmission means and one receiver, can be connected. The known circuit arrangement is directed to the task of simultaneously transmitting outgoing signals, receiving incoming signals and shielding the respective receiver of a station against signals going out from the transmitter of the same station, all via a single signal line by means of a driver circuit of a specific construction.